Optical pulse stretcher, laser apparatus, and electronic device manufacturing method

The present application is a continuation application of International Application No. PCT/JP2021/044119, filed on Dec. 1, 2021, the entire contents of which are hereby incorporated by reference.

The present disclosure relates to an optical pulse stretcher, a laser apparatus, and an electronic device manufacturing method.

Recently, in a semiconductor exposure apparatus, improvement in resolution has been desired for miniaturization and high integration of semiconductor integrated circuits. For this purpose, an exposure light source that outputs light having a shorter wavelength has been developed. For example, as a gas laser apparatus for exposure, a KrF excimer laser apparatus that outputs a laser beam having a wavelength of about 248 nm and an ArF excimer laser apparatus that outputs a laser beam having a wavelength of about 193 nm are used.

Spectral linewidths of spontaneous oscillation beams of the KrF excimer laser apparatus and the ArF excimer laser apparatus are as wide as from 350 μm to 400 μm. Therefore, when a projection lens is formed of a material that transmits ultraviolet light such as a KrF laser beam and an ArF laser beam, chromatic aberration may occur. As a result, the resolution may decrease. Given this, the spectral linewidth of the laser beam output from the gas laser apparatus needs to be narrowed to an extent that the chromatic aberration is ignorable. Therefore, in a laser resonator of the gas laser apparatus, a line narrowing module (LNM) including a line narrowing element (etalon or grating, etc.) may be provided in order to narrow the spectral linewidth. Hereinafter, a gas laser apparatus with a narrowed spectral linewidth is referred to as a line narrowing gas laser apparatus.

Patent Document 1: U.S. Pat. No. 6,067,311 Patent Document 2: Japanese Unexamined Patent Application Publication No. 2006-186046

An optical pulse stretcher according to one aspect of the present disclosure stretches a pulse width of a pulse laser beam, and includes a polarizer, a delay optical system, and a first Faraday rotator. The polarizer is configured to separate a component in a specific polarization direction of the pulse laser beam that has entered. The delay optical system includes a plurality of mirrors through which the pulse laser beam reflected by or transmitted through the polarizer is propagated. The first Faraday rotator includes a first magnet and a first Faraday material and is disposed on an optical path of the delay optical system to rotate a polarization direction of the pulse laser beam.

A laser apparatus according to another aspect of the present disclosure includes an oscillator and an optical pulse stretcher. The oscillator is configured to output a pulse laser beam. The optical pulse stretcher is configured to stretch a pulse width of the pulse laser beam. The optical pulse stretcher includes a polarizer configured to separate a component in a specific polarization direction of the pulse laser beam that has entered, a delay optical system including a plurality of mirrors through which the pulse laser beam reflected by or transmitted through the polarizer is propagated, and a first Faraday rotator that includes a first magnet and a first Faraday material and is disposed on an optical path of the delay optical system to rotate a polarization direction of the pulse laser beam.

An electronic device manufacturing method according to yet another aspect of the present disclosure includes generating a laser beam having a stretched pulse width with a laser apparatus, outputting the laser beam to an exposure apparatus, and exposing a photosensitive substrate to the laser beam in the exposure apparatus to manufacture an electronic device. The laser apparatus includes an oscillator configured to output a pulse laser beam, and an optical pulse stretcher configured to stretch a pulse width of the pulse laser beam. The optical pulse stretcher includes a polarizer configured to separate a component in a specific polarization direction of the pulse laser beam that has entered, a delay optical system including a plurality of mirrors through which the pulse laser beam reflected by or transmitted through the polarizer is propagated, and a first Faraday rotator that includes a first magnet and a first Faraday material and is disposed on an optical path of the delay optical system to rotate a polarization direction of the pulse laser beam.

1.1 Polarizer 1.2 TIS (Time-Integral Square) 1. Terms 2.1 Configuration 2.2 Operation 2.3 Problem 2. Overview of Laser Apparatus according to Comparative Example 3.1 Configuration 3.2 Operation 3.3 Example 1 of Control Flow 3.4 Example 2 of Control Flow 3.5 Effect 3.6.1 Configuration 3.6.2 Operation 3.6.3 Effect 3.6 Modification 1 3.7.1 Configuration 3.7.2 Operation 3.7.3 Effect 3.7 Modification 2 3. Embodiment 1 4.1 Configuration 4.2 Operation 4.3 Example of Control Flow 4.4 Effect 4.5.1 Configuration 4.5.2 Operation 4.5.3 Effect 4.5 Modification 1 4.6.1 Configuration 4.6.2 Operation 4.6.3 Effect 4.6 Modification 2 4. Embodiment 2 5. Modification of Laser Apparatus 6. Electronic Device Manufacturing Method 7. Others

Hereinafter, embodiments of the present disclosure will be described in detail with reference to the drawings. The embodiments described below show some examples of the present disclosure and do not limit contents of the present disclosure. In addition, all configurations and operations described in the embodiments are not necessarily essential as configurations and operations of the present disclosure. Here, the same components are denoted by the same reference numerals, and any redundant description thereof is omitted.

1.1 Polarizer

A polarizer refers to an optical element that separates light having a specific polarization direction (transmission axis direction) from light having a polarization direction orthogonal thereto. When the polarization direction of the light is inclined by 0 degrees with respect to the transmission axis of the polarizer, each polarization component is separated by a ratio of equations below. A relationship of the equations below is called Malus' law.

1 FIG. 1 FIG. is a graph illustrating an example of a relationship between an angle formed by a transmission axis of a polarizer and a polarization direction of incident light and a transmittance. In, a horizontal axis represents an angle θ formed by the transmission axis of the polarizer and polarized light, and a vertical axis represents the transmittance.

1.2 TIS (Time-Integral Square)

A TIS is an index representing a length of a pulse width of a laser beam, and is calculated from an equation below.

Here, I(t) represents light intensity per time.

2.1 Configuration

2 FIG. 2 2 10 50 60 70 schematically illustrates a configuration of a laser apparatusaccording to a comparative example. The comparative example of the present disclosure is an example recognized by the applicant as known only by the applicant, and is not a publicly known example admitted by the applicant. The laser apparatusincludes an oscillator, an optical pulse stretcher (OPS), a monitor module, and a laser control unit.

50 60 10 10 14 17 18 18 17 The OPSand the monitor moduleare disposed in this order on an optical path of a pulse laser beam output from the oscillator. The oscillatorincludes a chamber, a rear mirror, and an output coupling mirror. The output coupling mirrorand the rear mirrorare disposed to configure an optical resonator.

14 15 15 16 16 14 a b a b 2 The chamberis disposed on an optical path of the optical resonator, and includes a pair of discharge electrodesandand two windowsandthrough which a laser beam is transmitted. An excimer laser gas is introduced into the chamber. The excimer laser gas may include, for example, an Ar gas or a Kr gas as a rare gas, a Fgas as a halogen gas, and a Ne gas as a buffer gas.

50 52 54 54 54 54 52 52 52 52 2 a b c d The OPSincludes a beam splitterand concave mirrors,,, and, which form a delay optical path. The beam splitteris disposed on an optical path of the laser beam, and is coated with a film that transmits a portion of incident pulse laser beam and reflects the other portion of the pulse laser beam. A reflectance of the beam splitteris preferably about 60%. The beam splittercauses the pulse laser beam transmitted through the beam splitterto be output from the laser apparatusas described above.

54 54 54 54 54 54 52 52 54 54 52 54 54 8 a d a d a d a b c d f. The concave mirrors-have a substantially same focal length f. The concave mirrors-are disposed to have a following relationship. That is, the concave mirrors-are disposed such that an image of a laser beam reflected by the beam splitterat a position of the beam splitteris inverted by the concave mirrorand the concave mirrorand formed, then is returned to the beam splitteragain by the concave mirrorand the concave mirror, and is normally rotated and formed. In this case, a delay optical path length L is

60 62 63 63 63 70 The monitor moduleincludes a beam splitterand a photosensor. The photosensormay be, for example, a biplanar discharge tube or a photodiode. Data measured using the photosensoris transmitted to the laser control unit.

2.2 Operation

70 15 15 14 15 15 14 18 18 17 a b a b Based on control by the laser control unit, a high voltage pulse is applied between the discharge electrodesandin the chamberfrom an unillustrated power supply. When discharge occurs between the discharge electrodesandin the chamber, a laser gas is excited, and a pulse laser beam having an ultraviolet wavelength from 150 nm to 380 nm is output from the output coupling mirrorby the optical resonator configured by the output coupling mirrorand the rear mirror.

18 50 50 The pulse laser beam output from the output coupling mirrorenters the OPS, and a portion of the pulse laser beam passes through the delay optical path in the OPStwo or more times so as to be stretched to a predetermined pulse width.

50 62 2 50 62 63 63 60 70 A portion of the pulse laser beam having passed through the OPSis transmitted through the beam splitterand is output from the laser apparatus. The other portion of the pulse laser beam having passed through the OPSis reflected by the beam splitterand enters the photosensor. Pulse energy E is measured by the photosensor, and obtained data is transmitted from the monitor moduleto the laser control unit.

70 The laser control unitcontrols a voltage of the high voltage pulse output from the unillustrated power supply so that a difference ΔE between target pulse energy Et and the measured pulse energy E approaches 0.

2.3 Problem

50 [Method 1] Changing a circulating optical path length 52 [Method 2] Changing a reflectance of the beam splitter There are two methods of changing a pulse width or a pulse waveform stretched in the OPS, for example.

52 In Method 1, it is necessary to prepare in advance a plurality of kinds of standard products of OPS housings having different circulating optical path lengths. In Method 2, it is necessary to prepare in advance a plurality of kinds of standard products having different reflectances for the beam splitter. In addition, both Method 1 and Method 2 require replacement with the standard product, and replacement work needs a large amount of time and labor. Further, only a configuration of the prepared standard product can be changed, a degree of freedom of the change is low, and it is difficult to optimize the pulse width or the pulse waveform.

3 FIG. 3 FIG. 2 FIG. 2 2 schematically illustrates a configuration of a laser apparatusA according to Embodiment 1. The laser apparatusA illustrated inwill be described in terms of differences from the configuration illustrated in.

16 14 14 b The windowof the chambermay be disposed, for example, at a Brewster's angle. The pulse laser beam output from the chambermay be linearly polarized or randomly polarized.

2 51 50 51 91 54 54 91 54 54 91 91 2 FIG. a d b c The laser apparatusA includes an OPSinstead of the OPSin. In the OPS, a Faraday rotatoris disposed on the delay optical path formed by the concave mirrors-. The Faraday rotatoris disposed, for example, on an optical path between the concave mirrorand the concave mirror. The Faraday rotatormay be disposed anywhere on the delay optical path. The Faraday rotatoris preferably disposed on an optical path of collimated light.

52 53 51 53 2 FIG. Further, instead of the beam splitterin, a polarizeris disposed in the OPS. The polarizeris coated with a film that highly transmits P-polarized light and highly reflects S-polarized light.

91 95 96 95 96 2 The Faraday rotatorincludes a Faraday materialand a magnet. The Faraday materialmay be calcium fluoride (CaF) crystals or synthetic quartz. The magnetmay be a permanent magnet or an electromagnet.

4 FIG. 4 FIG. 4 FIG. 5 FIG. 4 FIG. 91 96 is a cross-sectional view illustrating details of a configuration of the Faraday rotator.illustrates a cross section parallel to an optical axis of the pulse laser beam. A center line CL inrepresents a center of the magnet.is a cross-sectional view taken along a 5-5 line in.

120 91 120 95 96 95 120 95 95 120 120 96 95 An actuatorconfigured to control a rotation amount in a polarization direction is disposed in the Faraday rotator. The actuatormay be, for example, a mechanism that moves the Faraday materialwith respect to the magnetin an optical axis direction of the pulse laser beam. A movable amount (maximum moving amount) of the Faraday materialby the actuatoris preferably half or more of a length in the optical axis direction of the pulse laser beam of the Faraday material. A minimum moving unit of the Faraday materialby the actuatormay be, for example, about 0.2 mm. The actuatormay be configured to move the magnetwith respect to the Faraday materialin the optical axis direction of the pulse laser beam.

91 95 96 120 The Faraday rotatoris an example of “first Faraday rotator” in the present disclosure. The Faraday materialand the magnetare examples of “first Faraday material” and “first magnet” in the present disclosure. The actuatoris an example of “first actuator” in the present disclosure.

120 95 96 96 96 91 The actuatoris not limited to a moving mechanism that relatively moves the Faraday materialand the magnet, and may be, for example, a mechanism that uses the magnetas an electromagnet and controls a current flowing through the electromagnet, or a mechanism that uses a heater or the like to control a temperature of the magnet. In the present specification, a term “actuator” is used as a term of a concept including not only a device that performs a mechanical operation but also a structure (mechanism) that can change the rotation amount in the polarization direction by the Faraday rotatorby changing a current, a temperature, or the like.

95 97 96 95 95 Since a shape of a cross section perpendicular to the optical axis of the pulse laser beam is a longitudinally long rectangle, a cross-sectional shape of the Faraday materialmay also be a longitudinally long rectangle. A cross-sectional shape of a magnetic field generating partof the magnetwhere the Faraday materialis disposed may be a longitudinally long rectangle in a same direction as the cross-sectional shape of the Faraday material.

95 97 96 100 100 95 100 101 102 The Faraday materialis disposed in the magnetic field generating partof the magnetwhile being held by a Faraday material holder. A shape of a cross section of the Faraday material holderperpendicular to the optical axis of the pulse laser beam may be a longitudinally long rectangle similar to that of the Faraday material. The Faraday material holderhas a through-holeformed at one end in a longitudinal direction of the longitudinally long rectangle and a female screw holeformed at the other end.

124 101 126 102 100 121 121 124 126 126 120 121 121 96 120 a b a b A guide shaftis inserted into the through-hole, and a rod-shaped male screwis screwed into the female screw hole. The Faraday material holderis held by a plateand a platevia the guide shaftand the male screw. The male screwis rotatably held and is connected to the actuator. The plateand the platealso hold the magnet. The actuatoris an example of “first moving mechanism” in the present disclosure.

3 FIG. 2 72 120 63 72 70 72 63 70 Further, as illustrated in, the laser apparatusA includes an OPS control unitthat controls the actuatorin response to a measurement result of the photosensor. The OPS control unitis connected to the laser control unit. The OPS control unitmay receive the measurement result of the photosensorvia the laser control unit.

70 72 72 70 70 72 Each of the laser control unitand the OPS control unitis configured using a processor. The processor of the present disclosure is a processing device including a storage device in which a control program is stored and a CPU (Central Processing Unit) that executes the control program. The processor is specifically configured or programmed to perform various kinds of processing included in the present disclosure. The processor may include an integrated circuit represented by an FPGA (Field Programmable Gate Array) or an ASIC (Application Specific Integrated Circuit). A processing function of the OPS control unitmay be incorporated in the laser control unit. Functions of the laser control unitand the OPS control unitmay be implemented by one or more processors.

95 91 95 95 When a pulse laser beam polarized in a specific direction is transmitted through the Faraday materialto which a magnetic field is applied, the polarization direction is rotated. The rotation amount in the polarization direction of the pulse laser beam in the Faraday rotatoris determined by intensity of the magnetic field, a physical quantity such as a refractive index that the Faraday materialhas, and a length of the Faraday material.

97 96 95 96 120 91 The intensity of the magnetic field of the magnetic field generating partof the magnetvaries depending on a position in the optical axis direction. Therefore, by changing the position in the optical axis direction of the pulse laser beam of the Faraday materialwith respect to the magnetby the actuator, it is possible to control the rotation amount of polarization of the pulse laser beam in the Faraday rotator.

10 53 53 51 53 53 51 Of the pulse laser beam polarized in a specific direction and output from the oscillator, a component parallel to a transmission axis of the polarizeris transmitted by the polarizer, and passes through the OPS. A component orthogonal to the transmission axis of the polarizeris reflected by the polarizerand is propagated through the delay optical path in the OPS.

6 FIG. 6 FIG. 6 FIG. 51 51 is an explanatory diagram illustrating an example of a polarization direction of a pulse laser beam entering the OPSand a polarization direction of a pulse laser beam having passed through the OPS. A double arrow indicated in a circle inrepresents the polarization direction of the pulse laser beam.illustrates the polarization direction of the pulse laser beam when viewed in a propagation direction of the pulse laser beam.

6 FIG. 10 53 51 10 53 51 As illustrated in, when the polarization direction of the pulse laser beam output from the oscillatorand the transmission axis of the polarizerare orthogonal to each other, all components of the pulse laser beam are reflected and are propagated through the delay optical path in the OPS. When the polarization direction of the pulse laser beam output from the oscillatorand the transmission axis of the polarizerare parallel to each other, all components of the pulse laser beam are transmitted and are not propagated through the delay optical path in the OPSso that stretching of a pulse width and change of a pulse waveform cannot be performed.

53 51 53 51 53 51 53 51 6 FIG. While the component of the pulse laser beam transmitted through the polarizerpasses through the OPSand the component of the pulse laser beam reflected by the polarizeris propagated through the delay optical path in OPSin, the component of the pulse laser beam transmitted through the polarizermay be propagated through the delay optical path in the OPS, and the component of the pulse laser beam reflected by the polarizermay pass through the OPS.

53 54 54 91 53 53 51 53 51 a b For the pulse laser beam reflected by the polarizer, the concave mirror, and the concave mirror, the polarization direction is rotated by the Faraday rotator. The pulse laser beam having the rotated polarization direction returns to the polarizer, and the component parallel to the transmission axis of the polarizeris transmitted and is propagated through the delay optical path in the OPSagain. The component orthogonal to the transmission axis of the polarizeris reflected and passes through the OPS.

It should be noted that a term “orthogonal” or “perpendicular” in the present specification, unless clearly described, is not limited to a case of being strictly orthogonal or perpendicular, and includes a concept of being substantially orthogonal or substantially perpendicular including a range of an angle difference that is practically allowable without losing technical significance, except for a case of being clear from context. In addition, a term “parallel” in the present specification, unless clearly described, is not limited to a case of being strictly parallel, and includes a concept of being substantially parallel including a range of an angle difference that is practically allowable without losing technical significance, except for a case of being clear from context.

72 120 91 72 120 95 91 63 95 The OPS control unitmay control the actuatorof the Faraday rotatorto change the rotation amount in the polarization direction. The OPS control unitmay control the actuatorso as to change the polarization direction by moving the Faraday materialin the optical axis direction by a predetermined moving amount, and may determine the rotation amount of the Faraday rotatorbased on the measurement result of the photosensorfor each position of the Faraday material.

54 54 54 54 51 54 54 54 54 a b c d a b c d The concave mirrors,,, andforming the delay optical path of the OPSare an example of “delay optical system” in the present disclosure. The concave mirrors,,, andare an example of “plurality of mirrors” in the present disclosure.

7 FIG. 7 FIG. 2 72 63 91 is a flowchart illustrating Example 1 of control processing in the laser apparatusA according to Embodiment 1.illustrates a flow in which the OPS control unitacquires a pulse waveform from the photosensor, calculates a pulse width (TIS), and controls the Faraday rotatorsuch that the TIS satisfies a target.

11 72 In step S, the OPS control unitreceives a target TIS. The target TIS may be received from, for example, a processing apparatus or an exposure apparatus which is not illustrated.

12 72 Thereafter, in step S, the OPS control unitissues a request for oscillation for target TIS setting.

13 72 13 72 13 In step S, the OPS control unitdetermines whether or not the oscillation for TIS setting is permitted. When a determination result in step Sis No determination, the OPS control unitrepeats step S.

13 72 14 14 72 1 14 8 FIG. When the determination result in step Sis Yes determination, the OPS control unitproceeds to step S. In step S, the OPS control unitperforms first TIS control. In the drawings, for example, the first TIS control is referred to as “TIS control”. A subroutine of the first TIS control applied to step Swill be described later with reference to.

15 14 72 In step Safter step S, the OPS control unittransmits a signal indicating an end of the target TIS setting.

15 72 7 FIG. After step S, the OPS control unitends the flowchart in.

8 FIG. 8 FIG. 7 FIG. 2 is a flowchart illustrating Example 2 of the control processing in the laser apparatusA according to Embodiment 1. The flowchart illustrated inmay be executed, for example, after the flowchart inis ended.

20 70 2 In step S, the laser control unitstarts an operation of the laser apparatusA.

21 72 21 72 22 22 25 12 15 7 FIG. In step S, the OPS control unitdetermines whether or not the target TIS has been received. When a determination result in step Sis Yes determination, the OPS control unitproceeds to step S. The respective steps from step Sto step Smay be similar to the corresponding steps from step Sto step Sin, and redundant description will be omitted.

26 25 70 2 26 21 In step Safter step S, the laser control unitdetermines whether or not to end the operation of the laser apparatusA. When a determination result in step Sis No determination, the processing returns to step S.

21 72 26 When the determination result in step Sis No determination, the OPS control unitproceeds to step S.

26 70 2 8 FIG. When the determination result in step Sis Yes determination, the laser control unitstops the laser apparatusA and ends the flowchart in.

9 FIG. 7 FIG. 8 FIG. 14 24 is a flowchart illustrating an example of a subroutine applied to step Sinor step Sin.

9 FIG. 30 72 95 96 95 95 95 96 When the flowchart inis started, in step S, the OPS control unitmoves a position in the optical axis direction of the Faraday materialwith respect to the magnetto an initial position. The position in the optical axis direction of the Faraday materialis defined by, for example, a center position of the Faraday material. The initial position of the Faraday materialmay be, for example, a center position of the magnet.

32 72 10 Next, in step S, the OPS control unitcauses the oscillatorto output a pulse laser beam.

33 72 63 In step S, the OPS control unitmeasures a pulse waveform by the photosensor.

34 72 95 Then, in step S, the OPS control unitcalculates a TIS from the measured pulse waveform, and stores a value of the calculated TIS in association with the position of the Faraday material.

36 72 95 36 72 37 95 37 33 Thereafter, in step S, the OPS control unitdetermines whether or not the position of the Faraday materialis a final moving position. When a determination result in step Sis No determination, the OPS control unitproceeds to step Sto move the Faraday materialin the optical axis direction. The moving amount at the time may be a predetermined moving amount such as 0.5 mm. After step S, the processing returns to step S.

36 72 38 When the determination result in step Sis Yes determination, the OPS control unitproceeds to step S.

38 72 In step S, the OPS control unitstops output of the pulse laser beam.

39 72 95 39 72 95 72 120 Thereafter, in step S, the OPS control unitmoves the Faraday materialto a position satisfying a target value (the target TIS) of the TIS. Instead of step S, the OPS control unitmay move the Faraday materialto a position where the TIS is the longest. The OPS control unitcontrols the actuatorso that the TIS becomes equal to or greater than the target value.

39 72 9 FIG. 7 FIG. 8 FIG. After step S, the OPS control unitends the flowchart inand returns to the flowchart inor.

10 FIG. 10 FIG. 2 95 91 is a flowchart illustrating a modification of TIS control in the laser apparatusA according to Embodiment 1. The flowchart inis an example of a method in which table data describing a relationship between the TIS and the position of the Faraday materialis created in advance and the Faraday rotatoris controlled based on the table data.

40 72 40 11 FIG. In step S, the OPS control unitperforms processing of creating and storing the table data. A subroutine of the processing applied to step Swill be described later with reference to.

40 41 72 After step S, in step S, the OPS control unittransmits an oscillation ready signal.

42 70 2 43 48 21 26 24 46 8 FIG. 8 FIG. 10 FIG. In step S, the laser control unitstarts the operation of the laser apparatusA. The respective steps from step Sto step Smay be similar to the corresponding steps from step Sto step Sin. However, instead of step Sin,includes step S.

46 72 46 12 FIG. In step S, the OPS control unitperforms second TIS control. A subroutine of the second TIS control applied to step Swill be described later with reference to.

11 FIG. 10 FIG. 40 is a flowchart illustrating an example of a subroutine of the processing applied to step Sin.

11 FIG. 9 FIG. 50 72 95 96 50 54 30 34 When the flowchart inis started, in step S, the OPS control unitmoves the position in the optical axis direction of the Faraday materialwith respect to the magnetto the initial position. The respective steps from step Sto step Smay be similar to the corresponding steps from step Sto step Sin.

55 54 72 95 In step Safter step S, the OPS control unitrecords the position of the Faraday materialand TIS data in the table data.

56 72 95 56 58 36 38 9 FIG. Thereafter, in step S, the OPS control unitdetermines whether or not the position of the Faraday materialis the final moving position. The respective steps from step Sto step Smay be similar to the corresponding steps from step Sto step Sin.

53 57 95 95 120 120 By repeating a loop from step Sto step S, the table data indicating the relationship between the position of the Faraday materialand the TIS is acquired. Since the position of the Faraday materialcorresponds to a control amount of the actuator, the table data may define a relationship between the TIS and the control amount of the actuator.

58 72 11 FIG. 10 FIG. After step S, the OPS control unitends the flowchart inand returns to the flowchart in.

12 FIG. 10 FIG. 12 FIG. 46 60 72 95 is a flowchart illustrating an example of a subroutine of the processing applied to step Sin. When the flowchart inis started, in step S, the OPS control unitreads a target position of the Faraday materialthat can achieve the target TIS from the table data.

61 72 120 95 Then, in step S, the OPS control unitdrives the actuatorso as to move the Faraday materialto the target position.

61 72 12 FIG. 10 FIG. After step S, the OPS control unitends the flowchart inand returns to the flowchart in.

51 51 By the OPSaccording to Embodiment 1, change to any pulse width (TIS) is possible without changing components of the optical system, such as changing the circulating optical path length or changing optical components. Further, by the OPSaccording to Embodiment 1, it is possible to satisfy the target value of the pulse width (TIS) without changing the components of the optical system.

13 FIG. 13 FIG. 3 FIG. 2 schematically illustrates a configuration of a laser apparatusB according to Modification 1 of Embodiment 1. The configuration illustrated inwill be described in terms of differences from the configuration illustrated in.

10 2 11 17 11 12 13 12 13 11 3 FIG. An oscillatorA of the laser apparatusB includes a line narrowing module (LNM)instead of the rear mirrorin. The LNMincludes a prism beam expanderfor narrowing a spectral linewidth, and a grating. The prism beam expanderand the gratingare disposed in Littrow arrangement in which an incident angle and a diffracting angle coincide with each other. The LNMis an example of “line narrowing optical system” in the present disclosure.

18 18 11 The output coupling mirroris a reflective mirror having a reflectance of 40% to 60%. The output coupling mirrorand the LNMare arranged to configure an optical resonator.

70 15 15 14 15 15 14 18 18 11 2 a b a b 3 FIG. Based on control by the laser control unit, a high voltage pulse is applied between the discharge electrodesandin the chamberfrom an unillustrated power supply. When discharge occurs between the discharge electrodesandin the chamber, a laser gas is excited, and a pulse laser beam having a line-narrowed wavelength being an ultraviolet wavelength from 150 nm to 380 nm is output from the output coupling mirrorby the optical resonator configured by the output coupling mirrorand the LNM. The remaining operation is the same as the operation of the laser apparatusA according to Embodiment 1 described with reference to.

2 By the laser apparatusB according to Modification 1 of Embodiment 1, it is possible to stretch the pulse width and change the pulse waveform of the pulse laser beam having a line-narrowed ultraviolet wavelength.

2 Further, according to the laser apparatusB, it is possible to change the pulse laser beam having a line-narrowed ultraviolet wavelength into any pulse width and pulse waveform without changing the components of the optical system.

14 FIG. 14 FIG. 3 FIG. 2 schematically illustrates a configuration of a laser apparatusC according to Modification 2 of Embodiment 1. The configuration illustrated inwill be described in terms of differences from the configuration illustrated in.

2 10 10 30 20 10 30 40 30 51 3 FIG. In the laser apparatusC, a part of the oscillatorinis configured by a system of an MOPO (Master Oscillator Power Oscillator) type including an oscillation stage laserA and an amplification stage laser. A MO beam steering unitis disposed between the oscillation stage laserA and the amplification stage laser, and a PO beam steering unitis disposed between the amplification stage laserand the OPS.

10 11 14 18 10 10 13 FIG. The oscillation stage laserA includes the LNM, the chamber, and the output coupling mirror. The configuration of the oscillation stage laserA may be the same as that of the oscillatorA described with reference to.

20 21 22 10 30 The MO beam steering unitincludes a high reflective mirrorand a high reflective mirror, and is disposed so that a pulse laser beam output from the oscillation stage laserA enters the amplification stage laser.

30 34 37 38 38 37 34 30 The amplification stage laserincludes a chamber, a rear mirror, and an output coupling mirror. The output coupling mirrorand the rear mirrorconfigure an optical resonator, and the chamberis disposed on an optical path of the optical resonator. The amplification stage laseris an example of “amplifier” in the present disclosure.

34 14 34 35 35 36 36 34 a b a b A configuration of the chambermay be the same as that of the chamber. The chamberincludes a pair of discharge electrodesandand two windowsand, and an excimer laser gas is introduced into the chamber.

37 38 The rear mirrormay be a partial reflection mirror having a reflectance of 50% to 90%. The output coupling mirrormay be a partial reflection mirror having a reflectance of 10% to 30%.

40 43 44 30 51 The PO beam steering unitincludes a high reflective mirrorand a high reflective mirror, and is disposed so that a pulse laser beam output from the amplification stage laserenters the OPS.

70 15 15 14 15 15 14 18 18 11 a b a b Based on control by the laser control unit, a high voltage pulse is applied between the discharge electrodesandin the chamberfrom an unillustrated power supply. When discharge occurs between the discharge electrodesandin the chamber, a laser gas is excited, and a pulse laser beam having a line-narrowed wavelength being an ultraviolet wavelength from 150 nm to 380 nm is output from the output coupling mirrorby the optical resonator configured by the output coupling mirrorand the LNM.

18 37 30 20 18 The pulse laser beam output from the output coupling mirrorenters the rear mirrorof the amplification stage laseras seed light via the MO beam steering unit. The pulse laser beam output from the output coupling mirroris an example of “first pulse laser beam” in the present disclosure.

37 34 35 35 34 35 35 34 38 37 38 a b a b At timing when the seed light transmitted through the rear mirrorenters the chamber, a high voltage pulse is applied between the discharge electrodesandin the chamberfrom an unillustrated power supply. When discharge occurs between the discharge electrodesandin the chamber, a laser gas is excited, the seed light is amplified by a Fabry-Perot optical resonator configured by the output coupling mirrorand the rear mirror, and an amplified pulse laser beam is output from the output coupling mirror.

30 51 40 51 The pulse laser beam output from the amplification stage laserenters the OPSvia the PO beam steering unit. The operation of the OPSis the same as that in Embodiment 1.

2 By the laser apparatusC according to Modification 2 of Embodiment 1, it is possible to stretch the pulse width and change the pulse waveform of the pulse laser beam having a line-narrowed ultraviolet wavelength and high energy.

2 Further, according to the laser apparatusC, it is possible to change the pulse laser beam having the line-narrowed ultraviolet wavelength and the high energy to any pulse width and pulse waveform without changing the components of the optical system.

15 FIG. 15 FIG. 3 FIG. 2 schematically illustrates a configuration of a laser apparatusD according to Embodiment 2. The configuration illustrated inwill be described in terms of differences from the configuration illustrated in.

2 202 51 202 205 206 202 91 4 FIG. 5 FIG. In the laser apparatusD, a Faraday rotatoris disposed upstream of the OPS. The Faraday rotatorincludes a Faraday materialand a magnet. A structure of the Faraday rotatormay be the same as a structure of the Faraday rotatordescribed with reference toand.

202 205 206 91 51 91 202 51 202 95 96 120 91 95 96 120 205 206 202 205 206 In the Faraday rotator, an unillustrated actuator that moves the Faraday materialwith respect to the magnetin the optical axis direction of the pulse laser beam is disposed. Hereinafter, for convenience of description, the Faraday rotatordisposed in the delay optical path of the OPSwill be referred to as a first Faraday rotator, and the Faraday rotatordisposed upstream of the OPSwill be referred to as a second Faraday rotator. In addition, the Faraday material, the magnet, and the actuatorof the first Faraday rotatorwill be referred to as a first Faraday material, a first magnet, and a first actuator, and the Faraday material, the magnet, and the actuator of the second Faraday rotatorwill be referred to as a second Faraday material, a second magnet, and a second actuator.

205 205 206 205 A maximum moving amount of the second Faraday materialby the second actuator is preferably half or more of a length in the optical axis direction of the pulse laser beam of the second Faraday material. A smallest moving unit of the second actuator may be, for example, about 0.2 mm. The second actuator may move the second magnetwith respect to the second Faraday materialin the optical axis direction of the pulse laser beam. The second actuator is an example of “second moving mechanism” in the present disclosure.

16 FIG. 202 51 is an explanatory diagram illustrating an example of a polarization direction of a pulse laser beam entering the second Faraday rotatorand a polarization direction of a pulse laser beam having passed through the OPS.

30 202 16 FIG. The polarization direction of the pulse laser beam polarized in a specific direction and output from the amplification stage laseris rotated by the second Faraday rotator.illustrates an example in which the polarization direction is rotated clockwise.

53 53 51 53 53 51 For the pulse laser beam having the rotated polarization direction, the component parallel to the transmission axis of the polarizeris transmitted by the polarizerand passes through the OPS. The component orthogonal to the transmission axis of the polarizeris reflected by the polarizerand is propagated through the delay optical path in the OPS.

53 51 53 51 53 51 51 16 FIG. While the component of the pulse laser beam transmitted through the polarizerpasses through the OPSand the component of the pulse laser beam reflected by the polarizeris propagated through the delay optical path in the OPSin, the component of the pulse laser beam transmitted through the polarizermay be propagated through the delay optical path in the OPSand the component of the reflected pulse laser beam may pass through the OPS.

53 91 51 91 53 53 51 53 53 51 For the pulse laser beam reflected by the polarizer, the polarization direction is rotated by the first Faraday rotatoron the delay optical path in the OPS. The pulse laser beam having the polarization direction rotated by the first Faraday rotatorreturns to the polarizer, and the component parallel to the transmission axis of the polarizeris transmitted and is propagated through the delay optical path in the OPSagain. Of the pulse laser beam propagated through the delay optical path and returned to the polarizer, the component orthogonal to the transmission axis of the polarizeris reflected and passes through the OPS.

16 FIG. 53 51 51 51 According to the configuration in, the polarization direction of 0-circulation light which is transmitted through the polarizerand is output from the OPSwithout circulating in the delay optical path of the OPSand the polarization direction of one-or-more-circulation light which is output from the OPSafter circulating in the delay optical path one or more times are different and the rotation amount of polarized light can be adjusted at two parts so that a degree of freedom in changing a pulse width or the like is further high as compared with the configuration of Embodiment 1.

72 120 91 72 202 The OPS control unitmay control the first actuatorof the first Faraday rotatorto change the rotation amount in the polarization direction. The OPS control unitmay control the second actuator of the second Faraday rotatorto change the rotation amount in the polarization direction.

72 91 63 72 202 63 72 202 2 72 91 2 The OPS control unitmay determine the rotation amount of the first Faraday rotatorbased on a measurement result by the photosensor. The OPS control unitmay determine the rotation amount of the second Faraday rotatorbased on a measurement result by the photosensor. The OPS control unitmay control the rotation amount of the second Faraday rotatorin order to change the waveform of a first half of the pulse waveform of the pulse laser beam output from the laser apparatusD. The OPS control unitmay control the rotation amount of the first Faraday rotatorin order to change the waveform of a second half of the pulse waveform of the pulse laser beam output from the laser apparatusD.

17 FIG. 17 FIG. 7 FIG. 2 is a flowchart illustrating an example of a control processing in the laser apparatusD according to Embodiment 2. The flowchart illustrated inwill be described in terms of differences from that illustrated in.

71 73 11 13 74 14 17 FIG. 7 FIG. 17 FIG. 7 FIG. Step Sto step Sinare similar to the corresponding steps that are step Sto step Sin. The flowchart inincludes step Sinstead of step Sin.

73 72 74 74 72 74 18 FIG. When a determination result in step Sis Yes determination, the OPS control unitproceeds to step S. In step S, the OPS control unitperforms third TIS control. A subroutine of the third TIS control applied to step Swill be described later with reference to.

75 74 15 75 72 7 FIG. 17 FIG. Step Safter step Sis similar to step Sin. After step S, the OPS control unitends the flowchart in.

18 FIG. 18 FIG. 17 FIG. 18 FIG. 74 95 1 96 1 205 2 206 2 is a flowchart illustrating an example of the third TIS control. The flowchart inis an example of the subroutine of processing applied to step Sin. In, for convenience of illustration, the first Faraday materialis referred to as “Faraday material”, the first magnetis referred to as “magnet”, the second Faraday materialis referred to as “Faraday material”, and the second magnetis referred to as “magnet”.

18 FIG. 9 FIG. 80 72 95 96 80 30 When the flowchart inis started, in step S, the OPS control unitmoves a position in the optical axis direction of the first Faraday materialwith respect to the first magnetto an initial position. Step Smay be similar to step Sin.

81 72 205 206 205 205 205 206 81 72 82 Next, in step S, the OPS control unitmoves a position in the optical axis direction of the second Faraday materialwith respect to the second magnetsto an initial position. The position in the optical axis direction of the second Faraday materialis defined by, for example, a center position of the second Faraday material. The initial position of the second Faraday materialmay be, for example, a center position of the second magnet. After step S, the OPS control unitproceeds to step S.

82 72 10 Next, in step S, the OPS control unitcauses the oscillatorto output a pulse laser beam.

83 72 63 84 72 95 205 In step S, the OPS control unitmeasures a pulse waveform by the photosensor. Then, in step S, the OPS control unitcalculates a TIS from the measured pulse waveform, and stores the value in association with the position of the first Faraday materialand the position of the second Faraday material.

86 72 95 86 72 87 95 86 87 36 37 87 83 9 FIG. Thereafter, in step S, the OPS control unitdetermines whether or not the position of the first Faraday materialis a final moving position. When a determination result in step Sis No determination, the OPS control unitproceeds to step Sto move the first Faraday materialin the optical axis direction. Step Sand step Sare similar to step Sand step Sin. After step S, the processing returns to step S.

86 72 90 90 72 205 90 72 91 95 When the determination result in step Sis Yes determination, the OPS control unitproceeds to step S. In step S, the OPS control unitdetermines whether or not the position of the second Faraday materialis a final moving position. When a determination result in step Sis No determination, the OPS control unitproceeds to step Sto move the first Faraday materialto the initial position.

92 72 205 92 83 Thereafter, in step S, the OPS control unitmoves the second Faraday materialin the optical axis direction. The moving amount at the time may be a predetermined moving amount such as 0.5 mm. After step S, the processing returns to step S.

90 72 94 94 72 When the determination result in step Sis Yes determination, the OPS control unitproceeds to step S. In step S, the OPS control unitstops output of the pulse laser beam.

96 72 95 205 96 72 95 205 Thereafter, in step S, the OPS control unitmoves the first Faraday materialand the second Faraday materialto positions satisfying a target value (the target TIS) of the TIS. Instead of step S, the OPS control unitmay move the first Faraday materialand the second Faraday materialto positions where the TIS is the longest.

96 72 18 FIG. 17 FIG. After step S, the OPS control unitends the flowchart inand returns to the flowchart in.

17 FIG. 18 FIG. 10 FIG. 11 FIG. 95 205 91 202 Without being limited to the flowcharts described inand, as in the example described inand, table data describing a relationship between the TIS and the position of the first Faraday materialand the position of the second Faraday materialmay be created in advance and the first Faraday rotatorand the second Faraday rotatormay be controlled based on the table data.

According to Embodiment 2, it is possible to stretch the pulse width and change the pulse waveform of the pulse laser beam without changing the components of the optical system such as changing a circulating optical path length or changing an optical component. Further, according to Embodiment 2, it is possible to satisfy the target value of the pulse width (TIS) without changing the components of the optical system.

51 53 53 53 53 51 51 53 When the polarization direction of the pulse laser beam entering the OPSis orthogonal to the transmission axis of the polarizer, all components of the pulse laser beam are reflected by the polarizerand are propagated through the delay optical path. Then, only the component of the pulse laser beam orthogonal to the transmission axis of the polarizeris reflected by the polarizerand passes through the OPS. Therefore, the pulse laser beam transmitted through the OPSis only the component orthogonal to the transmission axis of the polarizer(polarization purity is high). The configuration of Embodiment 2 can be applied to applications requiring the high polarization purity, such as a light source for an exposure apparatus.

19 FIG. 19 FIG. 15 FIG. 2 schematically illustrates a configuration of a laser apparatusE according to Modification 1 of Embodiment 2. The configuration illustrated inwill be described in terms of differences from the configuration illustrated in.

10 2 11 17 11 15 FIG. 13 FIG. The oscillatorA of the laser apparatusE includes the LNMinstead of the rear mirrorin. The configuration of the LNMmay be similar to that in.

10 2 10 2 13 FIG. 15 FIG. An operation of the oscillatorA of the laser apparatusE is similar to that of the oscillatorA in. The remaining operation is the same as the operation of the laser apparatusD according to Embodiment 2 described with reference to.

2 By the laser apparatusE according to Modification 1 of Embodiment 2, it is possible to stretch the pulse width and change the pulse waveform of the pulse laser beam having a line-narrowed ultraviolet wavelength.

2 Further, according to the laser apparatusE, it is possible to change the pulse laser beam having the line-narrowed ultraviolet wavelength to any pulse width and pulse waveform without changing the components of the optical system.

20 FIG. 20 FIG. 15 FIG. 2 schematically illustrates a configuration of a laser apparatusF according to Modification 2 of Embodiment 2. The configuration illustrated inwill be described in terms of differences from the configuration illustrated in.

2 10 10 30 20 10 30 40 30 51 19 FIG. In the laser apparatusF, the part of the oscillatorA inis configured by a system of an MOPO (Master Oscillator Power Oscillator) type including the oscillation stage laserA and the amplification stage laser. The MO beam steering unitis disposed between the oscillation stage laserA and the amplification stage laser, and the PO beam steering unitis disposed between the amplification stage laserand the OPS.

10 20 30 40 14 FIG. The configurations of the oscillation stage laserA, the MO beam steering unit, the amplification stage laser, and the PO beam steering unitmay be similar to those in.

2 2 An operation of the laser apparatusF is similar to the operation of the laser apparatusC.

2 By the laser apparatusF according to Modification 2 of Embodiment 2, it is possible to stretch the pulse width and change the pulse waveform of the pulse laser beam having a line-narrowed ultraviolet wavelength and high energy.

2 Further, according to the laser apparatusF, it is possible to change the pulse laser beam having the line-narrowed ultraviolet wavelength and the high energy to any pulse width and pulse waveform without changing the components of the optical system.

10 14 FIG. 19 FIG. Without being limited to the configuration of the oscillation stage laserA illustrated inand, for example, a solid-state laser system including a semiconductor laser and a wavelength conversion system may be employed. The wavelength conversion system may be configured using a nonlinear optical crystal. That is, an oscillation stage laser is not limited to a gas laser, and may be an ultraviolet solid-state laser that outputs a pulse laser beam having an ultraviolet wavelength. For example, the oscillation stage laser may be a solid-state laser that oscillates at a wavelength of about 193.4 nm, or an ultraviolet solid-state laser that outputs fourth harmonic light of a titanium-sapphire laser (wavelength of about 774 nm).

30 14 FIG. An amplifier is not limited to a configuration including a Fabry-Perot resonator such as the amplification stage laserillustrated in, and may be a configuration including a ring resonator. Further, the amplifier is not limited to a configuration including an optical resonator, and may be a simple amplifier such as an excimer amplifier. The amplifier may be a multi-pass amplifier such as a three-pass amplifier that performs amplification by reflecting seed light by a cylindrical mirror and making the seed light pass through a discharge space three times.

21 FIG. 80 80 804 806 2 80 804 2 806 schematically illustrates a configuration example of an exposure apparatus. The exposure apparatusincludes an illumination optical systemand a projection optical system. The laser apparatusA generates a laser beam and outputs the laser beam to the exposure apparatus. The illumination optical systemilluminates a reticle pattern of an unillustrated reticle disposed on a reticle stage RT with the laser beam which has entered from the laser apparatusA. The projection optical systemperforms reduction projection of the laser beam transmitted through the reticle and forms an image on an unillustrated workpiece disposed on a workpiece table WT. The workpiece is a photosensitive substrate such as a semiconductor wafer on which photoresist is applied.

80 2 2 2 The exposure apparatussynchronously translates the reticle stage RT and the workpiece table WT to expose the workpiece to the laser beam reflecting the reticle pattern. After the reticle pattern is transferred onto the semiconductor wafer by an exposure process described above, a semiconductor device can be manufactured through a plurality of processes. The semiconductor device is an example of “electronic device” in the present disclosure. Without being limited to the laser apparatusA, the laser apparatusesB-F or the like may be used.

The description above is intended to be illustrative and the present disclosure is not limited thereto. Therefore, it would be obvious to those skilled in the art that modifications to the embodiments of the present disclosure would be possible without departing from the scope of the claims. Further, it would be also obvious for those skilled in the art that the embodiments of the present disclosure would be appropriately combined.

The terms used throughout the present specification and the claims should be interpreted as non-limiting terms unless clearly described. For example, terms such as “comprise”, “include”, “have”, and “contain” should not be interpreted to be exclusive of other structural elements. Further, indefinite articles “a/an” should be interpreted to mean “at least one” or “one or more.” Further, “at least one of A, B, and C” should be interpreted to mean any of A, B, C, A+B, A+C, B+C, and A+B+C as well as to include combinations of any thereof and any other than A, B, and C.